I echo what the others have said.
For your specific current problem: stop by your local hardware store and pick up a black light (ultraviolet light) from the fluorescent lightbulb section, or stop by a pet store and get a flashlight-like device called a StinkFinder. Wait until dark, turn off all the lights, and wave the light over any suspect surfaces. Areas that have been urinated upon (and sometimes some other objects) will fluoresce in the light. That'll enable you to determine what areas may need more cleaning.
To get rid of the urine smell, use white vinegar. Some stores sell it in gallon jugs, which is what I think you'll be interested in. In my area, prices range from 1.89 to 3.29, so it can pay to shop around. Once you have the vinegar and have identified the area(s) needing treatment, splash vinegar over the area that needs to be cleaned and swirl it around a little. If the urine has been sitting there for a while, I'll usually let the vinegar sit for about five minutes, then I mop the vinegar up with a towel.
I throw the towels in the laundry with regular detergent and another cup of white vinegar, and they're fine too. I've also done t-shirts, pants, etc, with white vinegar. Thicker items like pillows or such might need a couple of cups of vinegar in the laundry cycle to clear the smell.
HTH --
Jean and her Gwyn